User Manual

Appendix
397
Step
Action
Description
F10
ACK—Proxy Server to User B
The proxy server sends the SIP ACK to User
B. The ACK confirms that the proxy server
has received the 200 OK response. The call
session is now active.
F11
BYE—User B to Proxy Server
User B terminates the call session by
sending a SIP BYE request to the proxy
server. The BYE request indicates that User
B wants to release the call.
F12
BYE—Proxy Server to User A
The proxy server forwards the SIP BYE
request to User A to notify that User B
wants to release the call.
F13
200 OK—User A to Proxy Server
User A sends a SIP 200 OK response to the
proxy server. The 200 OK response
indicates that User A has received the BYE
request. The call session is now terminated.
F14
200 OK—Proxy Server to User B
The proxy server forwards the SIP 200 OK
response to User B to indicate that User A
has received the BYE request. The call
session is now terminated.
Unsuccessful Call Setup—Called User is Busy
The following figure illustrates the scenario of an unsuccessful call caused by the called user’s
being busy. In this scenario, the two end users are User A and User B. User A and User B are
located at Yealink Skype for Business phones.
The call flow scenario is as follows:
1. User A calls User B.
2. User B is busy on the Skype for Business phone and unable or unwilling to take another
call.